Mike, I answer not as an aaaaaa but as someone that has spent many years looking at PP favs. This is what I found to work:

25% win + 50% place record (at least 5 starts)
less than 2000 metresonly
no 3kg claimers
a METRO win in last 4 starts, and absolute golden rule: Metro run last start!!
no jumps amatuer, female jocks only, or races for maidens and or fillies only
finished within 3.5 lengths of winner last start (within 21 days)
delete any horse carrying more than 60k'gs and/or more than 7 years old
rated at at least 97 (unitab)
placed at least once at todays distance and todays track conditions
8-12 runners only after scratchings

and lastly make sure you use the same source of PP fav at all times never mix,
i.e if sportsman always sportsman etc etc.

and absolute last ALWAYS bet at BEST TOTE/SP